Proline isomerism leads to multiple folded conformations of calbindin D9k: direct evidence from two-dimensional 1H NMR spectroscopy.

Chazin WJ, Kördel J, Drakenberg T, Thulin E, Brodin P, Grundström T, Forsén S
Proc Natl Acad Sci U S A. 1989 86 (7): 2195-8

PMID: 2928325 · PMCID: PMC286878 · DOI:10.1073/pnas.86.7.2195

A complete analysis of calbindin D9k by two-dimensional 1H nuclear magnetic resonance spectroscopy has established the existence of two conformations for the folded protein in solution. Well-resolved major and minor resonances in a ratio of 3:1 are observed throughout the 1H NMR spectrum. Two-dimensional exchange experiments show that the major and minor species are related by an equilibrium process. Analysis of short proton-proton distances along the peptide backbone, identified by two-dimensional nuclear Overhauser effect spectroscopy, provides unambiguous evidence that the two forms of the folded protein differ only in the isomerization state of the peptide bond between Gly-42 and Pro-43. Cis-trans isomerism of Pro-43 is thereby directly identified as the cause of multiple conformations for the folded protein in solution. In addition, when Pro-43 is mutated to a glycine residue there is no indication of multiple conformations. These results provide evidence for the possibility of conformational heterogeneity in the native state of globular proteins.

MeSH Terms (7)

Calbindins Hydrogen Isomerism Magnetic Resonance Spectroscopy Proline Protein Conformation S100 Calcium Binding Protein G

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